8 research outputs found
CRL4RBBP7 is required for efficient CENP-A deposition at centromeres
The mitotic spindle drives chromosome movement during mitosis and attaches to chromosomes at dedicated genomic loci named centromeres. Centromeres are epigenetically specified by their histone composition, namely the presence of the histone H3 variant CENP-A, which is regulated during the cell cycle by its dynamic expression and localization. Here, we combined biochemical methods and quantitative imaging approaches to investigate a new function of CUL4-RING E3 ubiquitin ligases (CRL4) in regulating CENP-A dynamics. We found that the core components CUL4 and DDB1 are required for centromeric loading of CENP-A, but do not influence CENP-A maintenance or pre-nucleosomal CENP-A levels. Interestingly, we identified RBBP7 as a substrate-specific CRL4 adaptor required for this process, in addition to its role in binding and stabilizing soluble CENP-A. Our data thus suggest that the CRL4 complex containing RBBP7 (CRL4(RBBP7)) might regulate mitosis by promoting ubiquitin-dependent loading of newly synthesized CENP-A during the G1 phase of the cell cycle
Aminomethylation of Michael Acceptors: Complementary Radical and Polar Approaches Mediated by Dialkylzincs
International audienc
Aminomethylation of Michael Acceptors: Complementary Radical and Polar Approaches Mediated by Dialkylzincs
International audienc
Kinetochores accelerate centrosome separation to ensure faithful chromosome segregation
At the onset of mitosis, cells need to break down their nuclear envelope, form a bipolar spindle and attach the chromosomes to microtubules via kinetochores. Previous studies have shown that spindle bipolarization can occur either before or after nuclear envelope breakdown. In the latter case, early kinetochore-microtubule attachments generate pushing forces that accelerate centrosome separation. However, until now, the physiological relevance of this prometaphase kinetochore pushing force was unknown. We investigated the depletion phenotype of the kinetochore protein CENP-L, which we find to be essential for the stability of kinetochore microtubules, for a homogenous poleward microtubule flux rate and for the kinetochore pushing force. Loss of this force in prometaphase not only delays centrosome separation by 5-6 minutes, it also causes massive chromosome alignment and segregation defects due to the formation of syntelic and merotelic kinetochore-microtubule attachments. By contrast, CENP-L depletion has no impact on mitotic progression in cells that have already separated their centrosomes at nuclear envelope breakdown. We propose that the kinetochore pushing force is an essential safety mechanism that favors amphitelic attachments by ensuring that spindle bipolarization occurs before the formation of the majority of kinetochore-microtubule attachments
Car câest moy que je peins
PlacĂ© sous lâinvocation de Montaigne, le prĂ©sent volume est le quatriĂšme ouvrage collectif offert aux lecteurs par les membres du Groupe de Recherches « Les Ă©crits du for privĂ© en France de la fin du Moyen Ăge Ă 1914 » (www.ecritsduforprive.fr). Cet ensemble dâĂ©crits ordinaires â mĂ©moires, autobiographies, livres de famille ou de raison, diaires, journaux intimes, chroniques ou annales â se dĂ©veloppe en Europe de la fin du Moyen Ăge Ă lâĂ©poque moderne, pour devenir un mode courant dâexpression au cours des XIXe et XXe siĂšcles. Ils sont parfois nommĂ©s Ă©crits « personnels » ou Ă©crits « intimes » et certains dâentre nous utilisent aussi, pour les dĂ©signer, le terme trĂšs significatif dâego-documents. Celui-ci renvoie fortement Ă lâidĂ©e que lâĂ©criture de ces textes nâest pas seulement une pratique qui pourrait ĂȘtre mise Ă distance par les scripteurs, mais quâelle influe profondĂ©ment sur la fabrique mĂȘme de la vie. Une relation puissante existe, en effet, entre de tels textes et lâidĂ©e que lâhomme occidental disposerait en lui-mĂȘme dâun espace de rĂ©flexion intĂ©rieure qui est gĂ©nĂ©ralement appelĂ© le « moi » ou le « soi ». Lorsquâil aborde un texte donnĂ©, le chercheur sait donc quâil part Ă la rencontre dâune individualitĂ©, celle du scripteur, dont il va chercher Ă explorer, Ă travers ses Ă©crits, non seulement les intentions apparentes dans les actions, ou affleurantes dans le langage, mais Ă©galement les mĂ©canismes de la pensĂ©e qui le constituent comme un individu au sein dâune sociĂ©tĂ© donnĂ©e. Ă travers un ensemble dâĂ©tudes de cas qui courent du Moyen Ăge au dĂ©but du XXe siĂšcle, nous avons ainsi souhaitĂ© explorer la relation complexe quâentretient ego avec lui-mĂȘme et son monde social, et ce Ă travers le prisme de ses Ă©crits privĂ©s